Disadvantages and Alternatives

Other fluorescence-based methods to investigate target-ligand interactions use fluorescence correlation spectroscopy (FCS) or fluorescence resonance energy transfer (FRET) [8, 12, 46]. 

However, the determination of affinity does not necessarily have to rely on labeled ligands. It is also possible with native ligands when using suitable detection methods, as for example nuclear magnetic resonance (NMR), surface plasmon resonance (SPR), acoustic biosensors or calorimetry [48, 49]. A particularly versatile and sensitive detection principle for the investigation of interactions between targets and native ligands is mass spectrometry [50]. 

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